首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   412733篇
  免费   5817篇
  国内免费   1386篇
电工技术   7704篇
综合类   349篇
化学工业   61994篇
金属工艺   14285篇
机械仪表   11871篇
建筑科学   11637篇
矿业工程   869篇
能源动力   11117篇
轻工业   43797篇
水利工程   3312篇
石油天然气   1835篇
武器工业   13篇
无线电   55388篇
一般工业技术   76614篇
冶金工业   74951篇
原子能技术   5568篇
自动化技术   38632篇
  2021年   2669篇
  2019年   2434篇
  2018年   3838篇
  2017年   3904篇
  2016年   4144篇
  2015年   3426篇
  2014年   5714篇
  2013年   19282篇
  2012年   10203篇
  2011年   14680篇
  2010年   11283篇
  2009年   12884篇
  2008年   13914篇
  2007年   14285篇
  2006年   12777篇
  2005年   11961篇
  2004年   11574篇
  2003年   11279篇
  2002年   10913篇
  2001年   11131篇
  2000年   10271篇
  1999年   10769篇
  1998年   24010篇
  1997年   17587篇
  1996年   13903篇
  1995年   10979篇
  1994年   9771篇
  1993年   9354篇
  1992年   7121篇
  1991年   6790篇
  1990年   6397篇
  1989年   6106篇
  1988年   5860篇
  1987年   4884篇
  1986年   4834篇
  1985年   5978篇
  1984年   5599篇
  1983年   4832篇
  1982年   4496篇
  1981年   4447篇
  1980年   4208篇
  1979年   4080篇
  1978年   3771篇
  1977年   4548篇
  1976年   6097篇
  1975年   3115篇
  1974年   3011篇
  1973年   2890篇
  1972年   2318篇
  1971年   2003篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
781.
This paper considers the evolution of the velocity and temperature fields within a jet of fluid on a thermally insulated wall. Numerical solutions are obtained for a range of Prandtl numbers and for a class of initial velocity and temperature profiles relevant to intrusion jets observed in certain thermal cavity flows. Numerical results are compared with asymptotic solutions which describe the initial structure of the jet and its subsequent diffusion at large distances downstream.  相似文献   
782.
This paper develops and demonstrates by computer simulations new nonlinear system stochastic techniques to determine the amplitude-domain and frequency-domain properties of nonlinear systems as described in nonlinear differential equations of motion. From measurements of input excitation data and output response data, this new method, based upon multiple-input/single-output (MI/SO) linear analysis of reverse dynamic systems, allows for the efficient identification of different nonlinear systems. Nonlinear systems simulated here include Duffing, Van der Pol, Mathieu, and Dead-Band systems. Features of this new method are: (1) it can be implemented using established MI/SO linear procedures and computer programs; (2) it determines nonlinear system amplitude properties separate from nonlinear system frequency properties; (3) it quantifies relative contributions from different nonlinear terms by using appropriate coherence functions; (4) it gives results that are independent of the input or output probability distributions, spectral properties, and input excitation levels.  相似文献   
783.
784.
785.
Two hundred twenty-eight patients with successful coronary stent implantation were randomized either to protamine administration and femoral sheath removal (group I, n = 117) or no heparin neutralization and delayed sheath removal (group II, n = 111). The hospital stay after treatment was shorter in patients receiving protamine; therefore, protamine use for neutralizing circulating heparin may be safely administered immediately after stent implantation.  相似文献   
786.
Two chronic haemodialyzed patients with digitalis intoxication are reported. One of them took digoxin 0.25 mg three times daily for an unknown period and the other took digitoxin 0.1 mg twice daily for two weeks. The symptoms of intoxication were mainly concealed by uremic syndrome. The diagnosis was established by noticed sinus bradycardia, first- and second-degree atrioventricular block in ECG and the determination of sera levels of glycosides (serum digoxin concentration was 7.36 ng/ml, serum digitoxin concentration was 46.5 ng/ml) in both cases. Considering the probable long elimination period of digitalis and the potentially life-threatening situation the patients were given digoxin-specific antibody (Fab) fragments with potassium replacement therapy. The symptoms disappeared within a few hours after therapy, side effects and rebound toxicity did not develop. In connection with these cases the aim of this report is to publish a method which can reverse the life-threatening digitalis intoxication in patients suffering from renal failure as well. As to the above method, the authors have not found any similar case reports in the Hungarian medical literature.  相似文献   
787.
We consider the task of partitioning the zeros of a real or complex polynomial into clusters and of determining their location and multiplicity for polynomials with coefficients of limited accuracy. We derive computational procedures for the solution of this task which combine symbolic computation with floating-point arithmetic. The validation of the existence ofmzeros in a specified small disk is described.  相似文献   
788.
789.
An optimal design for the RLSA (radial line slot array) antenna useful for DBS reception is presented. Classical geometries and structures given in the literature are first used. It is found that in some cases these are not suitable. So, optimization techniques by using the right objective functions have been applied. Two different methods were developed and three antennas were designed. Numerical results and comparisons with other similar antennas give the advantages of our design  相似文献   
790.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号